A recent post-hoc analysis of data from the PIONEER I and PIONEER II clinical trials indicates that C-reactive protein (CRP) levels may serve as a predictive biomarker for adalimumab response in patients with hidradenitis suppurativa (HS). The study, led by Alexa B. Kimball, MD, MPH, suggests that individuals with elevated CRP levels may experience a less robust response to adalimumab therapy.
The analysis, published in JAMA Dermatology, included 588 participants from the original PIONEER trials who had completed the study and had available laboratory data at baseline and week 12. The researchers defined elevated CRP as levels exceeding 0.30 mg/dL. The primary objective was to assess the association between CRP levels and clinical response to adalimumab.
CRP as a Biomarker in HS
The study revealed that 78.9% of participants had elevated CRP levels at baseline, with a median level of 1.23 mg/dL (IQR, 0.65–2.81 mg/dL). Patients with elevated CRP had a significantly higher mean BMI (34.1 vs 28.6; P < .001) and presented with more severe disease, as indicated by Hurley stage.
Impact on Adalimumab Efficacy
The analysis demonstrated a significant association between baseline CRP elevation and diminished odds of achieving a clinical response (OR, 0.53; 95% CI, 0.34–0.83). While adalimumab treatment was associated with greater odds of clinical response in both those with elevated CRP (OR, 3.18; 95% CI, 2.13–4.81) and those with normal CRP levels (OR, 2.25; 95% CI, 1.06–4.88), the researchers noted that among those with increased baseline CRP, each unit rise in CRP level corresponded to slightly diminished odds of clinical response (OR, 0.99; 95% CI, 0.97–1.00).
Specifically, the researchers estimated that subjects with a baseline CRP of 2.81 mg/dL had a 30% decrease in odds of response compared to subjects with a baseline CRP level of 0.30 mg/dL (OR, 0.70; 95% CI, 0.49–0.97).
Clinical Implications
"Our findings suggest that adalimumab may be less effective in patients with the most severe inflammatory load," the authors wrote. They suggest that clinicians treating non-responders might consider weight-based dosing of adalimumab, checking drug levels, or trialing alternative biologics.
The study's findings highlight the potential utility of CRP as a biomarker to guide treatment decisions in HS patients. Further research is needed to determine optimal CRP cutoffs and to explore alternative treatment strategies for patients with high CRP levels who may not respond adequately to adalimumab.
